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The Tropical Outlooks from the National Hurricane Center in Miami, FL and Central Pacific Hurricane Center in Honolulu, HI show multiple potential threats in the tropics. Images: NHC/CPHC

The National Hurricane Center (NHC) and Central Pacific Hurricane Center (CPHC) are tracking four tropical cyclone threats in their respective hurricane basins today and some may have direct impacts on the US coastline over time.
The threat closest to the United States today is a disturbance approaching Hawaii. Showers and thunderstorms associated with a broad area of low pressure located less than 800 miles southeast of Hilo, Hawaii have become slightly better organized. Environmental conditions appear to remain conducive for additional development of this system during the next few days as it drifts toward the west-northwest. The CPHC believes there’s a high chance of tropical cyclone formation and believe a tropical depression can form later today or tonight. Over time, this system could approach the island of Hawaii and the rest of the state, and residents and visitors there should closely monitor that system. If a tropical storm forms here, it would be called Walaka.

Potential Tropical Cyclone #9 may become Tropical Storm or perhaps Hurricane Harvey over time as it travels west through the Caribbean. Image: NHC

While a tropical depression is organizing near Hawaii, another one is developing near the Lesser Antilles promoting the NHC to begin issuing updates on Potential Tropical Cyclone #9. Satellite imagery, including experimental 1-minute data from GOES-16, indicates that the circulation of the low pressure area east of the Lesser Antilles is becoming better defined, and that a cluster of strong convection has formed just west of the center. The potential exists for this system to become a Tropical Storm soon; if it were to be named, it would be called Harvey. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the system this afternoon, and it is likely the aircraft will find a tropical cyclone has formed.

This tropical cyclone is forecast by the NHC to move off to the west; residents and visitors in the Caribbean should keep a watchful eye on it. A deep-layer ridge to the north of the system should steer it generally just north of due west through the next several days; as such, this storm is forecast to pass through the Lesser Antilles and into the eastern Caribbean Sea in 24-36 hours, into the central Caribbean by 72 hours, and to the western Caribbean by 4-5 days.

The NHC has low confidence in the future strength of this system due to conflicting model guidance. The system is in an area of moderate easterly vertical shear, and the large-scale models suggest that light/moderate shear should continue through the forecast period. This seems favorable for strengthening, and the SHIPS and LGEM models show slow, but steady, intensification. However, the American GFS and European ECMWF models forecast the system to degenerate to an easterly wave over the central Caribbean Sea, possibly due to dry air entrainment.

Current view of the entire half of the globe shows activity increasing in the tropics in both the Atlantic and Pacific hurricane basins. Image: NOAA

Beyond what could be Walaka and Harvey, the National Hurricane Center is tracking two other systems in the Atlantic Ocean that could become tropical cyclones this week.

Shower activity associated with an area of low pressure located about 1200 miles east of the Leeward Islands continues to show signs of organization. Gradual development of this system is possible during the next day or so while it moves west-northwestward at near 20 mph. After that, upper-level winds are expected to become less conducive for development. The NHC says there’s a 60% chance that this system will form into a tropical cyclone either over the next 48 hours or over the next 5 days.

A tropical wave located over the far eastern Atlantic Ocean near the Cabo Verde Islands is producing disorganized showers and thunderstorms. Gradual development of this system is possible during the next several days while it moves westward to west-northwestward at about 15 mph. For now, the NHC believes there’s a low chance of formation, pegging the odds at 30% for tropical cyclone formation over the next 5 days. Nevertheless, the system needs to be watched, especially beyond the 5-day forecast period.

Before any threat arrives on US shores, residents should make sure their Hurricane Action Plan is in order.

A tropical cyclone could be forming south and east of Hawaii over the next five days. Image: CPHC

While Hurricane Gert spins about east of the New Jersey shore, eyes are on the central Pacific where the next US tropical cyclone threat may arrive. Meteorologists at the Central Pacific Hurricane Center (CPHC) in Honolulu, which is part of the National Weather Service office there, are keeping a close eye on a system that is getting better organized south and east of Hawaii’s Big Island.

According to the CPHC, showers and thunderstorms associated with a broad area of low pressure about 800 miles southeast of Hilo, Hawaii remain disorganized early this morning. However, the CPHC says that environmental conditions appear to be conducive for gradual development of this system during the next few days as it moves slowly toward the northwest. The CPHC pegs the chance of tropical cyclone formation at 60% for the next 48 hours and a high 80% within the next 5 days.

Systems in the Central Pacific, between 140W and 180W, are monitored by the CPHC rather than the National Hurricane Center in Miami. Should a storm in the eastern Pacific form and move into the CPHC domain, it will keep the name the National Hurricane Center issues it and take on advisories once it crosses 140W. However, when a storm develops between 140W and 180W, the CPHC uses their own list of rotating names that are more appropriate for the region there.

Should a tropical cyclone develop and be named here, it would be called Walaka. Beyond Walaka, the next names to be used by the CPHC are Akoni, Ema, Hone, Iona, Keli, and Lala.

The latest Tropical Outlook from the National Hurricane Center shows numerous potential threats in the Atlantic beyond Hurricane Gert.

While Hurricane Gert spins about in the Atlantic between the US East Coast and Bermuda, things are becoming very active in the Atlantic as we approach the peak weeks of the Atlantic Hurricane season with a train of threats building. The National Hurricane Center (NHC) is tracking three disturbances which could become tropical cyclones in the coming days. Some long range computer forecast guidance is also suggesting that at least one of these systems could become a landfalling hurricane threat on the US coastline in just over a week from now.

An elongated area of low pressure located more than a thousand miles east of the Lesser Antilles is producing disorganized showers and thunderstorms. This system is expected to move westward at 15 to 20 mph across the tropical Atlantic Ocean, crossing into the Caribbean Sea on Friday. Environmental conditions appear somewhat supportive of tropical cyclone formation over the next few days but should become less favorable once the system moves into the Caribbean Sea. The chance of formation is low over the next 48 hours, with the NHC forecasting only a 20% chance of tropical cyclone formation here. Those odds increase to 40% over the next 5 days.

A second area of low pressure, associated with a tropical wave, is also producing disorganized shower and thunderstorm activity a few hundred miles west-southwest of the Cabo Verde Islands. Environmental conditions could be conducive for some slow development of this system over the next few days while it moves westward to west northwestward at 15 to 20 mph. According to the NHC, chance of tropical cyclone formation here is 10% over the next 48 hours and 20% for the next five days.

A tropical wave over western Africa is forecast to emerge over the far eastern Atlantic Ocean on Wednesday. Conditions appear conducive for some development after that time while the wave moves westward to west northwestward at about 15 mph. The NHC says development is unlikely over the next 48 hours and only 20% through the next five days.

The next tropical cyclone to be named in the Atlantic will be called Harvey.

Before any threat arrives on US shores, residents should make sure their Hurricane Action Plan is in order.

The National Hurricane Center (NHC) has upgraded Tropical Storm Gert to hurricane status, making it the second hurricane of the 2017 Atlantic Hurricane Season.vAt 11:00pm ET, the center of Hurricane Gert was located near latitude 31.2 North, longitude 72.3 West. Gert is moving toward the north near 8 mph and the NHC expects a turn toward the northeast with an increase in forward speed late Tuesday or Tuesday night. Maximum sustained winds have increased to near 75 mph, with some higher gusts. The NHC is forecasting some strengthening during the next 48 hours. Hurricane-force winds extend outward up to 25 miles from the center and tropical-storm-force winds extend outward up to 105 miles. The estimated minimum central pressure is 986 mb (29.12 inches).

Gert is forecast to pass between the US East Coast and Bermuda; while a direct hit is not expected, an indirect hit with rough surf and swells is. Swells generated by Gert will spread northward along the east coast of the United States from North Carolina northward to Long Island during the next couple of days. Swells are also expected to affect Bermuda during the next couple of days. These swells and rough seas will produce rip current conditions along much of the US East Coast; everyone should exercise extreme caution if entering the Atlantic Ocean and follow the guidance and posted signs/flags by local officials and lifeguards.

Latest Tropical Outlook map from the National Hurricane Center shows Tropical Storm Gert and another area that could develop into a tropical cyclone over the next 5 days. Map: NHC

Tropical Storm Gert continues to gain strength in the Atlantic and is forecast to become a hurricane soon; meanwhile, the National Hurricane Center (NHC) continues to watch a new disturbance which may pose an even larger threat to the United States as Hurricane Harvey.

Tropical Storm Gert is now moving toward the north. Very little change has been made to the NHC track forecast. Gert should continue to move around the western periphery of the subtropical ridge for the next day or so, before rapidly accelerating eastward ahead of a trough.

Despite the presence of moderate northerly vertical wind shear, there is good agreement among the intensity guidance that Gert will continue to strengthen for the next 48 hours. The NHC forecast gives more weight to the modest intensification scenario proposed by various forecast models and officially calls it to become a hurricane soon.

Current satellite loop of Gert. Image: NOAA

All of the global models show extratropical transition beginning in just under 2 days and completing in about 3, After extratropical transition completes, Gert is still expected to steadily weaken before being absorbed by a larger extratropical low in about 4 or 5 days.

While Gert is not expected to directly impact the US East Coast nor Bermuda, rough surf and rip currents are expected to make their way to both coasts this evening. Swimmers and boaters from New England south to Florida should exercise extreme caution when entering the Atlantic.

Meanwhile, while Gert spins up between the US East Coast and Bermuda, eyes are on a new disturbance in the far Atlantic. Showers and thunderstorms associated with an elongated area of low pressure located several hundred miles west-southwest of the Cabo Verde Islands have changed little in organization since this morning. Environmental conditions are expected to be generally conducive for development during the next several days while the disturbance moves westward at about 15 mph over the tropical Atlantic. While the chance of formation is low at about 30% for the next 48 hours according to the National Hurricane Center, the chance of formation over the next 5 days is high at 60%.

Many global forecast models, including recent runs of the European ECMWF, American GFS, and Canadian GEM, have suggested that this new disturbance will become a potent tropical cyclone, with some runs in recent days suggesting it would landfall on the US as a hurricane. While the storm is at least a week away from nearing US waters, and it is too soon to put much faith in extended guidance at this time, it is important that people anywhere on the US East Coast or Gulf Coast have a hurricane action plan prepared.

Should this disturbance in the Atlantic become a named tropical cyclone, it would be called Harvey.

Tropical Storm Gert has formed; the meteorologists at the National Hurricane Center (NHC) upgraded Tropical Depression #8 to the Atlantic Hurricane Season’s newest storm in their 5pm advisory. According to the NHC, satellite images indicate that the tropical cyclone is gradually strengthening and that banding features have become better established during the last several hours. The NHC also pointed out that the system has become less vertically tilted, showing a better organized tropical cyclone.

Gert is moving north-northwestward at 9 kt on the southwestern periphery of a subtropical ridge. A northward motion is expected tonight and Monday while the system rounds the western side of the ridge, and Gert is expected to be about midway between Bermuda and North Carolina on Monday and Tuesday. After that time, a progressively faster motion to the northeast and east-northeast is forecast as the system moves on the north side of the ridge and becomes embedded in the mid-latitude westerlies until it dissipates in about 5 days.

Gert is over warm 29 deg C sea surface temperatures and it will remain over these warm waters during the next few days. In addition, the global models indicate that the upper-level pattern should become conducive for strengthening during the next 36 hours or so. The combination of these conditions should allow Gert to strengthen during the next couple of days. Thereafter, a sharp increase in west-southwesterly shear, drier air, and decreasing sea surface temperatures should end the strengthening trend and lead to extratropical transition in a little more than 3 days.

The latest Tropical Outlook from the National Hurricane Center shows TD#8, likely to become Gert today. Also on the map: a tropical disturbance over the far Atlantic that may become Harvey over time. Map: NHC

Tropical Depression #8 formed yesterday and is expected to be upgraded and named Gert today; meanwhile, the National Hurricane Center is monitoring a new disturbance over the far Atlantic; should that system be named, it would become Harvey after Gert.

Tropical Depression #8 is forecast to move north-northwestward to northward for the next 36 hours around the western portion of a deep-layer subtropical ridge that is oriented east-west along 30-32N latitude. In about 2 days, a vigorous shortwave trough currently located over the northern Plains is expected to dig east-southeastward and weaken the ridge along the east coast of the United States from the Carolinas northward to New England. The increasing southwesterly flow ahead of the trough is forecast to accelerate the cyclone northeastward, on an optimal track about midway from the U.S. and Bermuda and keeping it away from those two land masses.

While the storm system will remain off-shore, rough seas and rip tide currents are possible along the US East Coast. Even though a direct impact is not expected at all, these indirect impacts could be hazardous and people visiting beaches from Florida to Massachusetts should exercise caution. Cruise ship passengers between the US East Coast and Bermuda should also expect rough seas.

The depression is expected to remain in a relatively low vertical wind shear environment for the next 24-36 hours, but also within a fairly dry mid-level moisture environment for the next few days. As a result, only modest strengthening is expected during the next couple of days. By Tuesday, southwesterly vertical wind shear is expected to steadily increase ahead of the aforementioned shortwave trough, which should act to cap any additional intensification.

A storm of greater consequence may be forming in the far Atlantic. A tropical wave that has just emerged off the west coast of Africa is forecast to move westward over the next couple of days and merge with a broad area of low pressure located southwest of the Cabo Verde Islands. Thereafter, environmental conditions are expected to be conducive for gradual development of the system while it moves westward to west-northwestward at 10 to 15 mph over the open tropical Atlantic Ocean.

Some global computer forecast models that aid meteorologists with their weather forecasting are quite bullish on this system over time. Both the American GFS and European ECMWF forecast this system to become a tropical cyclone over time. Some guidance also suggests that this system could become a hurricane and make landfall along the US East Coast. However, any such event is many days away; the most aggressive model brings this storm ashore no earlier than August 23. It is important to point out that long-range guidance around tropical cyclones has a huge margin of error and any one solution, landfall or not, shouldn’t be etched in stone so far in the future.

The next tropical cyclone to be named after Gert would be called Harvey.

Tropical Depression #8 has formed, according to the National Hurricane Center (NHC.) Late afternoon GOES-16 visible satellite images showed that the circulation associated with the low pressure located northeast of the Bahamas had become better defined. Since that time, the
night-time microphysics RGB product and other infrared satellite pictures have continued to show an improvement in the circulation, and recent ASCAT data show that the system has acquired a well- defined center. Deep convection is organized in a large curved band, however the center is located near the western edge of the band. The NHC reports that a NOAA buoy located southeast of the center reported 25 to 30 kt winds earlier this evening, and the scatterometer data support an initial wind speed of 30 kt.

Official track for Tropical Depression #8 from the National Hurricane Center. Map: NHC

While it looks like this tropical cyclone is on a collision course with the East Coast of the United States, the weather pattern should steer it out to sea. The depression is moving north-northwestward at this time and the depression should move north-northwestward to northward around the western side of a deep-layer ridge over the central Atlantic through Sunday night. It is expected to reach the mid-latitude westerlies by late Monday and begin to accelerate northeastward ahead of a short-wave trough that will be approaching the northeastern United States.

While the track is clear, the intensity forecast isn’t. The system is expected to pass over warm water and remain in a low-shear environment during the next day or so, but intrusions of dry mid-level air are likely to limit strengthening. Some computer guidance suggests a period in which the storm will gain significant strength, while others aren’t nearly as robust. The NHC forecast is currently an average of those intensity forecasts. While the system will gain strength in the short term, it is likely to become extratropical in 3 to 4 days.